CA1142030A

CA1142030A - Piston-pump

Info

Publication number: CA1142030A
Application number: CA000354051A
Authority: CA
Inventors: Bernhard Frey
Original assignee: Hydrowatt Systems Ltd
Current assignee: Hydrowatt Systems Ltd
Priority date: 1979-06-20
Filing date: 1980-06-16
Publication date: 1983-03-01
Also published as: US4671743A; DE3070978D1; JPS5627086A; HU183151B; EP0021315A1; ATE51683T1; ATE14915T1; AU5935080A; JPS6365830B2; SU1380617A3; BR8003711A; CS229656B2; EP0153982A2; JPH0250358B2; DE3072177D1; CH645435A5; ZA803580B; DD151487A5; PL130376B1; EP0021315B1

Abstract

A B S T R A C T O F T H E D I S C L O S U R E

In piston driven machines and in particular those having an elastically deformable sealing tube between the piston and the cylinder, which causes a relatively large structural length of the cylinder-piston arrangement and which may be provided with a forced feed for the lubricant, a reduction in the space requirement, in particular the structural length of the cylinder-piston arrangement is achieved by a driving mem-ber slidably mounted on a tubular cylinder externally and ex-tending over at least part of the length of the cylinder, and frictionally connected to a rotating driving mechanism. A
pulsating secondary space formed by the driving member at the outside of the cylinder is connected for the avoidance of shock pressures because of filling with lubricant liquid flo-wing away, through a balancing channel of large cross-section-al area to a pressure-balancing chamber. For further reduc-tion in the space requirement the often necessary lubricant cooling may be effected by means of a heat exchanger to which the lubricant and the working medium of the piston machine are admitted and which is arranged advantageously inside a lubri-cant storage chamber or collector.

Description

2~

The invention relates to piston driven machines, and more particularly to a piston-pump, having at least one cylinder and piston arrangement defining a pulsating working space, more par-ticularly, the invention relates to a piston-pump having a flex-ibly deformable sealing member which serves to seal the workingspace and which relies upon a liquid, namely a lubricant, for sliding movement against a bearing surface, and wherein a driving mechanism, in particular a rotary driving mechanism is provided for the piston. Machines of this kind are known, for example, from West German O/S 2S 54 733.

Piston-pumps of the type generally provided with a crank or eccentric drive are fundamentally burdened by comparatively costly structural and spacial requirements for the driving mechanism in relation to the usa~le swept volume. This applies in par~icular to known piston-pumps having an elastically deformable sealing tube because in continuous service the deformation due to stretching of the sealing material during the stroke amounts to only a fraction of the length of tube. The structural length of the cylinder-piston arrangement relative to the usable swept volume is thus quite high. Devices of this type ~' ' .~

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3~

wherein an elastically deformable sealing -tube is supported by means of pressure lubrication are subjec~ to similar di~ficul-ties. There exists therefore a need in the case of piston ma-chines in general and in particular piston-pumps of the kind 5 mentioned above, for a reduction in space requirements, as far as possible withou~ any essential increase in the structural outlay and whilst preserving a comparatively simple construc-tion.

An object of the invention is -therefore to proviae a 10 piston d~iven machine which is distinguished:by a cylinder-piston comparatively short structural length of the arrangement inclusive of the ad]oining parts of the driving mechanism. The solution of this problem is to be found in the invention claimed in Claim 1. The construction claimed therein comprises a dri-15 ving member, for example, a plunger or the like, to surround thecylinder. The driving member cooperates with an eccentric dri-ving mechanism, to produce oscillatory movement to correspond with the working motion. The driving member is of generally the same length as the cylinder for bearing and guidance of this 20 driving member. This permits a considerable shortening of the structural length of the cylinder-piston arrangement. The sec~
tion of the driving member which surrounds the cylinder is rela-tively thin-walled, permitting the entire cylinder-piston ar-rangement to avoid having a diameter of unduly large dimensions.
25 The reduction in the stxuctural length of the cylinder-piston arrangement becomes particularly noticeable in the case of star-shaped multi-cylinder arrangements, because this structural 3~

length reduces the overall diameter of the pump.
Thus, in accordance with the invention, there i5 provided a piston-pump comprising at least one cylinder-piston arrange-ment defining a pulsating working space, said cylinder-piston arrangement providing a flexibly deformable tubular sealing member, which serves to seal the working space, said tubular sealing member being adapted to bear slidably, via a liquid lubricant against a bearing surface, and a rotary driving mechanism provided for driving the piston, comprising a driving member extending externally over at least part of the length of the cylinder to embrace the cylinder, the driving member being adapted to be set in oscillatory motion by the driving mechanism.
. .
In the case of constructions of the presentkind there is defined a pulsating secondary space on the outside o~ the portion of the cylinder enclosed by the driving member and this secondary space pulsates in correspondence with the oscilla-ting working motion of the driving member. Thus, when a con-ventional piston-cylinder arrangement is used, seepage of lubricant from the working space is discharged into the secon-dary space. Alternatively the working space may be sealed by means of the aforementioned elastically deformable sealing tube supported by pressure lubrication. With a view to solving the problems of the carrying away of the liquid, an advanta-geous further development of the invention provides for at least one balancing channel of large cross-sectional area be-tween the pulsating secondary space and a pressure-balancing chamber. Shock pressures inside the cylinder-piston arrangement are thereby avoided in a simple way and even relatively large quantities of lubricant are carried away. In that case an existing s~brage chamber forlubricant or conveying medium is advantageously provided as the pressure-balancing chamber for-the pulsatingsecondary spacefor thecarryingaway of 3C~

circulating lubricant or other leaking conveying medium out of the working space.

As an extension of the above-described features, a further feature of the invention provides that the pulsa-ting secondary space is connected through a choke channelto a space which lies at the end of the cylinder inside the ariving member and pulsates in correspondence with the oscillating working motion. Through this construction the pulsating space between the end of the cylinder and the driving member in which is collected the lubricant escaping ~rom the cylinder or from the sealing tube or alternatively the seepage from the working space, is employed as a pumping or auxiliary working space for the continuous ejection of the liquid which is collected therein. In this case the choke channel in a particularly simple way restricts the return of the liquid from the secondary space relieved of pressure at the other end of the driving member to a small amount. Hence the choke channel acts as a non-return valve.

Another feature of the invention which may be applied particularly advantageously in combination with the pre-viously menti~ned~eatures of the invention, but if necessary also independently of them in the case of other kinds of motors or pumps e.g., piston motors or pumps, is a forced-feed lubrication system such as may be employed in particu-lar for the lubrication and support of an elastically de-formable sealing tube in the case of its sliding motion against a bearing surface. In the case of a machine having forced-feed lubrication which comprises a pressure lubrica-tion pump, a return collector, a return pump and a storage chamber feeding the pressure lubrication pump, this further feature of the invention is charac-terized by a bypass ~ .

~2~)3~

channel connecting the storage chamber -to the xeturn collec-tor and having an adjustable or controllable correcting member for restriction o~ the flow from the storage chamber to the return collector. This construction in a simple way enables reliable filling and thereby satisfactory operation of the return pump and hence the maintenance of the lubricant pressure essential to the overall safety in operation. This is particularly significant in the case o~ high-pressure pumps having lubricated sealing tubes, because a breakdown of the 10` lubrication at the bearing s-urface may very quickly have damage to the sealing tube as a result.

Piston driven machines of the present kind, having high power-densities demand special measures for reliable lubri-cation of -the highly loaded bearing points and the sliding surfaces of the piston. To this end this is accomplished by a forced-feed lubrication provided with a lubricant cooling device. The object of the invention, namely, primarily the reduction of the space requirement while maintaining a compara-tively low structural outlay extends accordingl~ also to the 20 construction of the forced-feed lubrication and in particu-lar the cooling device, because these structural elements, above all the cooling device normally have comparatively large`dimensions.

With a view to overcoming the prohlems relating to the 25 forced-feed lubrication and the cooling device it is in accor-dance with the invention that the cooling device is provided 33~

with at least one heat exchanger to which the lubricant and the working medium of the machine are admitted. In this way not only can the usual costly and spatially large devices for the admission to coolers or heat exchang~rs o~ external cooliny me~
dia, say, outside air set in motion by a fan, be saved, but on the contrary particularly advantageous possibilities of integra-tion of such a heat exchanger into the machine housing also re-sult, from which follows a further saving of space. Xn that case it proves particularly advantageous to arrange the heat exchanger in the region of a lubricant storage chamber or col lector of the forced-feed lubrication.

A further feature of the invention relates to pumps in which a prefeed pump for pressure-feeding the working medium to the inlet side of the pump is provided. A particularly inten-sive exchange of heat between the working medium and the lubri-cant is produced when, in accordance with another feature of the invention the working medium inlet side of the heat exchan-ger is connected to the outlet side of the prefeed pump, which permits reducing the space for the cooling device. The existing prefeèd pump is thereby used for forced circulation of the cooling working medium in the lubricant heat exchanger~ In this connection a particularly advantageous result is obtained by ~he construction of the working medium system of the heat exchanger as a return flow branch between the outlet side and the inlet side of the prefeed pump. In order to keep the return flow of the workin~ medium within proper limits, in accordance with an advantageous refinement of the invention, a choke, preferably - - \
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an adjustable choke, may be arranged in the hea~ exchanger re-turn flow branch.

Several embodiments of the invention will now be described in detail by way of example only with reference to the accom-panying drawings, in which:

Figure 1 is an axial section through a piston pump in accordance with the invention, having a star-shaped multi-cylinder arrangement with an eccentric drive;

Figure 2 illustrates the basic circuitry of the.lubrication sys-tem of the pump of Figure l;

Figure 3 is an axial elevation on a larger scale of a return pump of the lubrication system of the pump or Figure l;

Figure 4 .is a partial section of the pump runner of the return pump of Fi.gure 3, along the plane of section IV-IV; and Figure 5 is a partial axial sec~ion through the pump, similar to Figure 1, but with a modified region of the prefeed pump and of the lubricant storage chamber with the heat ` exchanger inserted; and Figure 6 is a cross-section through the pump in the region of the lubricant storage chamber with a heat exchanger, along the plane of section VI~VI in Figure 5.

Referring to Figure 1, the driving mechanism 10 of the pump consists of a rotary shaft 1 coupled to a motor (not shown) and r~

~2~3~1 having an eccentric member 2 mounted for rotation therewith. A
non-rotating slidepiece 3 is supportably mounted upon the eccen-tric member for reciprocating movement in response to rotation of the eccentric member. A piston 20 and a driving member 30 tangentially positioned in relation to the slidepiece define therebetween a pressure area 4. It will be understood that in the case of a pump having a plurality of pistons and cylinders, for example, five, there will be a corresponding number of pres-sure areas 4. In Figure l such a pressure area is shown in operative connection with a driving member 30 of a piston 20 which is connected to an elastically deformable sealing tube 22.
A spiral spring 23 forces the piston 20 against the bottom se~-tion 30b of the sleeve-shaped driving member 30 and puts the ! sealing tube under axial tensile prestress. The sealing tube is seated in the bore of a cylinder 25 to which it is firmly connected at the top end, and hence hermetically seals the working space 24 formed inside the tube. This working space alters its volume to correspond with the oscillating motion of the driving member 30 and in combination with non-return valves 26 and 27 which are connected to a delivery and suction channel 2~, generates the pump action.

The lubrication system of the pump is a forced-feed lubri-cation system with a pressure lubrication gear pump 100, a re-turn collector 120 surrounding the eccentric 3 of the driving mechanism and an annular stoxage chamber 110 surrounding concen-trically the axis XX of rotation of the driving mechanism, as well as a return pump 105 which delivers out of the return col-3~
_9_ lec-tor 120 into the storage chamber 110. This construction and arrangement of the storage chamber makes possible a particularly space-saving multi cylinder pump construction having symmetrical distribution of the connections to the individual cylinders round the circumference of the ring. The integration of the storage chamber into the cylindrical housing of the star-shaped multi-cylinder arrangement also serves the same purpose.

The pressuxe lubrication pump 100 delivers out of the sto-rage chamber 110 via channels 103 and 104 as well as a filter 102 into an annular distributor channel 101 out of which pres-sure channels 90 and 95 having adjustable chokes 90a and 95a respectively lead to the individual cylinders. The lubricant li~uid under pressure from the channel 90 is fed to the support of the sliding motion of the outer face of the sealing tube 22 15 and flows down in the direction axial to the cylinder (downwards in accordance with Figure 1) into a pulsating space 42 formed in the region of the bottom end of the piston and cylinder. This space is connected via a choke channel 45 which is made as a clearance volume between the inner face of the cylindrical sec-20 tion 30a of the driving member 30 and the outside of the cylin-der 25, to a likewise pulsating secondary space 35 formed at the top end of the cylindrical section 30a. In this way the lubri-cant liquid flowing down in the space 42, relieved of pressure, is delivered into the secondary space 35 via the choke channel 25 45 acting almost as a non-return valve, so that the space 42 acts essentially as a low-pressure space for undisturbed flowing-down of the lubricant out of the clearance volume between the 2~3~) -10~

sealing tube and the cylindrical bore or bearing surface respec-tively. For this automatic discharge pumping action low-pres-sure is moreover also necessary in the secondary space 35. For that purpose the latter is connected via a balancing channel 40 S of large cross-sectional area to the storage chamber 110 wliich hence serves as a pressure-balancing chamber.

The lubricant fed via the channel 95 arrives at the outer face of the cylindrical section 30a of the driving member 30, the latter being guided to be able to slide coaxially with re-spec~ to the cylinder 25. The lubrican~ then flows via lubri-cant channels 47 to ~he pressure areas 4 and on into the return collector 120. This lubricant circuit is also thereby closed.

. . . : . .

The return pump 105 via a channel 115 sucks out of the bottom part` of the collector 120 and delivers via a rising re-turn channel 106 into the region llOa at the crown of the sto-rage chamber 110. An effective deaeration of the flow of lubri-cant entering the stora~e chamber thereby results. For reliable filling of the return pump a bypass channel 130 is provided, ` which connects the suction space of the pump, i.e., the bottom part of the collector 120, to the storage chamber llO to pre-vent this space from being sucked empty. For restriction oE
the bypass a correcting member is provided, for which purpose, for example, an adjustable choke 135a may be adequate. In the case of the example, on the contrary, bypass regulation with a controllable valve 135 as the correcting member and a float 140 as the regulaking device is provided. ~'his allows khe mainten-~, ' 3~

ance of an optimum state of fill in the suction space of thereturn pump 105. ~dequate filling of the return pump is essen-tial in particular also for the avoidance of the formation of ~oam which would impair reliable forced-feed lubrication.

In Figure 2 the forced-feed lubrication system of the pump is reproduced diagrammatically in a clear form, the essential operational components being shown symbolically but with the same reference numbers as are provided in Figure 1.
.

As already mentioned, the avoidance of the formation of foam in the delivery system of the forced-feed lubrication is essential for satisfactory operation. This purpose is served in particular by the construction illustrated in ~igures 3 and

4 of the rotor 105a of the return pump 105 with a plurality of slits made as pressure chambers lOSb which are arranged after the style of a radial centrifugal pump and extend along a dif-ference in radius with respect to ~he axis of rotation XX of the pump The lubricant lying in these pressure chambers undergoes because of the heavy centrifugal forces a separation between lubricant having a high and low liquid content respectively or vice versa a low and high gas or foam content. In the region of a discharge control opening 108 extending round less than 180, in the case of suitable retardation or throttling of the dis-charge from the pump, essentially only that part of the lubri-cant is ejected radially out of the pressure chambers lOSb, which exhibits only a very low gas or foam content. Subsequently the pressure chambers come into connect:ion with a discharge con-~ - ~ ~
L2~3~

trol opening ].09b which accep~s the par-t of the lubricant which is rich in gas or foam and returns it into the collector 120 via a discharge channel lO9c not shown in greater detail. In the region between the discharge control openings 108 and lO9b which as shown in Figure 3 extend in like manner round an angle of considerably less than 180, the pressure chambers 105b are closed at their outer ends by an inner face 107 of the housing, so that this part of the rotation is available for separation of the portions of lubricant of different densities without dis-turbance because of through-flowO

A further mechanism which contributes to the gas and foam separation inside the rotor of the return pump is indicated in Figure 4. According to Figure 4, by means of a comparatively wide clearance volume lO9a arranged axially next to the rotor 105a and here shown of a greatly distorted size, a radial cir-cular flow may be generated with a pattern indicated at A, which favours the collection of the lubricant low in gas in the radi-ally outer regions of the pressure chambers 105b and if necessary also brings about or favours a parkial return in the direction towards the suction space in the pump, of the foam collected in the radially inner regions of the storage chambers.

It should be noted in particular that the compact construc-tion of the pump as shown in Figure 1, is further made possible . . by the provision of a prefeed pump 150 which permits the working 25 medium of the pump to be accommodated inside the annular lubri~
cant storage chamber 110 arranged at the endface of the cylinders .~ ~ 25.

3~) In the operation of the pump illustrated in E'iyures 5 and 6 a cooling device for the lubricant, designated as a whole by 20-0, is accommodated inside the annular lubricant storage cham-ber 110. This cooling device consists essentially of a heat exchanger 210 which exhibits a channel system 212 which can be seen in detail from Figure 6 and through which flows the working medium of the pump. The flow of the working medium in this channel system is achieved by means of the prefeed pump 150 al-ready mentioned, which is accommodated coaxially with the annu-lar storage chamber 110 as well as by axial overlapping in itsinner recess 140. The inlet side 160 of the prefeed pump 150 lies in the region of an axial end cover 155 of the pump hou~
sing which lines up with an endwall 230 closing off the storage chamber 110. The prefeed pump is in the case of the example made as an axial-flow pump the rotor of which in the way which may be seen diagrammatically from Figure 5 is seated on the pump shaft 1 and the outlet side 170 of which is connected by radial channels 172 to an annular channel 174. Axial branch channels 176 lead from the latter (in Figure 5 only on~ of these channels is shown) to the individual pump cylinders (not shown in greater detail) arranged in the form of a star. In this way the cylinder-piston arrangements of the pump obtain the working medium at an inlet pressure of, for example, a few atmospheres gauge which is adequate for reliable filling during the suction stroke of the piston.

Sections 178 of the channels prolonged towards the rear connect the outlet side 170 of the prefeed pump 150 to an annu-2~3~

lar channel 180 in a central section 232 of the endwall 230 in-serted like a cover. A radial channel 182 leads from the annu-lar channel 180 to an inlet distributor 216 of the heat exchan-ger 210, inserted in the outer part of the endwall 230~ From this inlet distributor arranged in the lower crest region of the storage chamber 110 the partial flow of the cool working medium branched off from the outlet side of the prefeed pump arrives via a channel system 212 in the heat exchanger 210, which may be seen in detail from Figure 6, at an outlet collector 218 arranged in the upper crest region crown of the s~orage chamber 110, i.e., diametrically opposite the inlet distributor 216. The outlet collector is likewise inserted in the outer part of the endwall 230. The outlet collector is connected via a radial channel 184 ! to the suction side 160 of the prefeed pump. ~ence there re-sults for the branched-off portion of the discharge flow from the prefeed pump 150 a return circuit in parallel with the main discharge flow, which is led to the inlet side of the main pump.
In order to be able to adjust the bridging and the pressure ratios of the prefeed pump 150 suitably, taking into considera-tion the return circuit, a throttle-screw 220 is inserted in the endwall 230, the tip of which engages in the channel 182 and forms here an adjustable choke point in the partial discharge flow to the inlet distributor 216.

Referring now to.Figure 6,` the construc-tion of the heat exchanger can be seen in detail. The channel system 212 of the heat exchanger lies practically completely immersed in~ide the lubricant storage chamber 110 and below the surface o~ the lubri-. ~ .

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zl~)3~

cant. Because of the opening of -the return flow channel 106 from the lubricant return pump 105 into the upper region 110a at the crown of the storage chamber 110 and the suction by the pressuxe lubrication purnp 100 in the bottom region of the crown a lubricant flow results in the annular storage chamber, which runs essentially in both circumferential directions from the up-per region at the crown downwards to the lower region of the crown. This flow is evidently directed in the opposite sense to the flow of working medium in the channél system of the heat exchanger 210 between the lower inlet distributor 216 and the upper outlet collector 218. Thus there results between the lubricant throughput in the storage chamber 110 on one side and the flow of working medium in the channel system of ~he heat exchanger 210 on the other side a transfer of heat in contra-flow and hence intensive cooling of the lubricant by the freshlyentering working medium.

For the construction of the heat exchanger the following applies in detail with reference to Figure 6: The channel system 212 of the heat exchanger 210 comprises a plurality of annular heat exhanger tubes 214 which extend in the direction circumferential to the storage chamber 110 and which - as al-ready mentioned - lie essentially below the surface of the lu-bricant and therefore enable exchange of heat over their whole surface. On both sides o~ the inlet distributor 216 and the outlet collector 218 a plurality of heat exchanger tubes 214 is in each case connected, which are connected in parallel with one another and made arched to fit the annular shape of the storage 2~334~

chamber 110. The result is an essentially cylindrical arrange-ment of heat exchanger tubes lying side by side in the direction axial to the cylinder, i.e., an arrangement of heat-transfer surfaces of large area adapted to the spatial proportions of the storage chamber and to the lubricant flow.

Evidently for this intensively acting heat exchange arrange-ment there is no additional space requirement because the whole arrangement is accommodated inside the existing lubricant storage chamber. The annular form of the last mentioned cha~ber enables not only space-saving integration into the overall structure of the machine housing but forces flow of lubricant in the direc-tion circumferential to the storage chamber along the heat ex-changer tubes in the sense of the contraflow cooling.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A hydraulic machine comprising at least one cylinder-piston arrangement defining a working space of variable volume, said cylinder-piston arrangement comprising a tubular sealing member which is flexibly stretchable in its longitudinal direction and sealingly connected at a first circumferentially extending portion of its tubular body to said cylinder and at a second circumferentially extending portion of its tubular body to said piston hermetically sealing said working space, there being provided a bearing surface adjacent to the surface of said tubular sealing member which is located opposite to said working space, the tubular body of said seal-ing member being supported via a lubricant by said bearing surface against the pressure in said working space, the machine further comprising a drive member which has a cylindrical sleeve portion and a bottom portion connected with said piston so as to impart to said piston a movement relatively to said cylinder in order to vary said working space volume, the sleeve portion of said drive member being shaped so as to enclose the cylinder of said cylinder-piston arrangement and extending externally over at least part of the length of said cylinder and of said tubular sealing member, said sleeve portion of the drive member being guided in relation to said cylinder coaxial-ly with the relative movement between said cylinder and said piston.

2. A hydraulic machine as claimed in Claim 1, wherein the drive member is guided along an exterior portion thereof for sliding movement in the direction longitudinal to the cylinder.

3. A hydraulic machine as claimed in Claim 1, wherein the drive member is in the shape of a sleeve having a cylindrical section to enclose the cylinder of the corresponding piston said driving member being frictionally coupled by its bottom section to the driving mechanism.

4. A hydraulic machine as in Claim 3, wherein a pulsating secondary space formed at the outside of the cylinder by the driving member to correspond with the oscillating working motion is connected via at least one balancing channel of large cross-sectional area to a pressure-balancing chamber.

5. A hydraulic machine as claimed in Claim 4, wherein the pulsating secondary space communicates via a choke channel with a space which lies at the end of the cylinder inside the driving member, said secondary space pulsating in correspondence with the oscillating working motion.

6. A hydraulic machine as claimed in Claim 5, wherein the choke channel is formed by a clearance volume between the inner face of the driving member and the outside of the cylinder.

7. A hydraulic machine as claimed in Claim 5 or Claim 6, wherein the pressure-balancing chamber for the pulsating secondary space includes a storage chamber for lubricant or conveying medium.

8. A hydraulic machine having at least one cylinder-piston arrangement for the formation of a pulsating working space, as claimed in Claim 1, further comprising forced-feed lubrication which comprises a pressure lubrication pump, a return collector, a return pump and a storage chamber feeding the pressure lubrication pump, characterized by a bypass channel connecting the storage chamber to the return collector.

9. An apparatus according to Claim 8, further comprising a bypass channel having an adjustable or controllable correcting member for restriction of the flow from the storage chamber to the return collector.

10. An apparatus according to Claim 9, characterized in that for the return collector a regulating or control device is provided for the maintenance of a minimum filling and that this control or regulating device is in operative connection with the correcting member for the flow in the bypass channel.

11. A piston-pump machine having at least one cylinder-piston arrangement and a rotary driving mechanism for the formation of a pulsating working space, as claimed in Claim 10, having forced-feed lubrication which includes a storage chamber or collector connected to the lubricant return, characterized in that the storage chamber or collector is annular and surrounds the axis of rotation of the driving mechanism and is concentric with the latter.

12. An apparatus as claimed in Claim 11, characterized in that the plane of the ring of the storage chamber or collector is arranged essentially vertically and that a return channel connected to the return pump is provided, which opens out into the region of the crown of the annular storage chamber or collector.

13. An apparatus as claimed in Claim 12, made as a star-shaped multi-cylinder arrangement characterized in that the annular storage chamber or collector is arranged at the end of and coaxial with the star-shaped multi-cylinder arrangement in a common housing with it.

14. A piston-pump for liquid working media having at least one cylinder-piston arrangement for the formation of a pulsating working space, having forced-feed lubrication according to Claim 13, comprising a lubricant cooling device which includes at least one heat exchanger to which the lubricant and a working medium are admitted.

15. An apparatus as claimed in Claim 14, in which the forced-feed lubrication comprises a storage chamber or collector connected to the lubricant return, characterized in that the heat exchanger is arranged in the region of the lubricant storage chamber or collector.

16. An apparatus as claimed in Claim 15, characterized in that the heat exchanger comprises a channel system through which flows the working medium and is arranged inside the lubricant storage chamber or collector.

17. An apparatus as claimed in Claim 16, characterized in that the channel system of the heat exchanger comprises a plurality of annular heat exchanger tubes which extend in the direction circumferential to the lubricant storage chamber or collector and the outer faces of which are at least partially in contact with the lubricant.

18. An apparatus as claimed in Claim 17, characterized in that the channel system of the heat exchanger comprises at least two connections arranged diametrically opposite one another in the annular lubricant storage chamber or collector, one of them being an inlet disbributor and the other an outlet distributor, and that in each case a plurality of heat exchanger tubes connected in parallel with one another runs in both circumferential direcions from the inlet distributor in the shape of an arc to the outlet distributor.

19. An apparatus as claimed in Claim 18, characterized in that the heat exchanger tubes running in the shape of an arc in the direction circumferential to the storage chamber or collector form an essentially cylindrical arrangement of tubes lying side by side in the direction axial to the cylinder.

20. An apparatus as claimed in Claim 19, characterized in that the throughput of working medium in the storage chamber or collector on one side and the flow of lubricant in the heat exchanger on the other run at least by sections in contraflow.

21. A pump as in Claim 20, having a prefeed pump feeding the working medium to the inlet side of the pump, characterized in that the working medium inlet side of the heat exchanger is connected to the outlet side of the prefeed pump.

22. An pump as claimed in Claim 21, characterized in that the working medium system of the heat exchanger is made as a bypass flow branch between the outlet side and the inlet side of the prefeed pump.

23. An pump as claimed in Claim 22, characterized in that at least one adjustable choke is provided in the heat exchanger bypass.

24. A pump as in Claim 23, characterized in that the annular lubricant storage chamber or collector is arranged to be at least approximately coaxial with the prefeed pump which is made as an axialflow machine, and to overlap this axially.

25. A pump as in Claim 18, 22 or 24 characterized in that the inlet distributor and the outlet collector are inserted into an axial endwall of the lubricant storage chamber or collector and connected via channels running in this endwall to the inlet and outlet sides respectively of the prefeed pump.